• Polymer(Korea)
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• v.34 no.1
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• pp.1-7
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• 2010

To enhance the transport properties of gas separation membrane, we prepared 6FDA-6FpDA based polyimide membrane with PMMA-graft-silica nanoparticles. The silica was grafted PMMA which is miscible with 6FDA-based polyimide after surface treatment by 3-methacryloxypropyltrimethoxysilane ($\gamma$-MPS). The untreated silica/6FDA-6FpDA membrane showed greater permeability and less selectivity than PMMA-g-silica/6FDA-6FpDA due to its low dispersion. The transport properties of PMMA-g-silica/6FDA-GFpDA membrane were measured as a function of filler concentration. These membranes were evaluated using pure gases (He, $O_2$, $N_2$, $CO_2$). The increase in permeation was attributed to changes in the free volume distribution until 1 wt%. After 1 wt%, the permeability was decreased by excess silica which decreased effective area in polymer matrix. The selectivity was decreased with increasing permeability on the whole. However, the selectivity of $CO_2$ showed more enhance value.

• Resources Recycling
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• v.16 no.5
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• pp.31-35
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• 2007

The formation of silica sol from sodium silicate solution and the growth of silica sols were investigated in this study. The $SiO_2$ content of 2% in sodium silicate solution was proper to oxidize sodium silicate with sulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicate solution had to be controlled above 9 for a stable silicate solution. The silica sol, which size is about 10 nm, could be prepared by heating the mixed solution of sodium silicate and silicate solution removed sodium ions at pH 10 and 80. And the silica sol grew into about 50 nm as silicate solution was added to silica sol solution.

• Journal of Convergence for Information Technology
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• v.8 no.5
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• pp.45-50
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• 2018

The functional nanomaterials of fluorescent dye-doped silica nanoparticles(NPs) are applied to bio applications such as bio-labeling of DNA micro-array, and bio-imaging. Organic dye-doped fluorescent silica NPs exhibit excellent bio-compatibility, non-toxic, and highly hydrophilic properties. In this study, organic fluorescent dyes were dissolved in ethanol, and deionized(DI) water. Organic fluorescent dyes were physically adsorbed to silica NPs and chemically doped to silica NPs. The fluorescence characteristics(FLC) was investigated by UV lamp irradiation of 365 nm wavelength. As results, the FLC of dye-doped silica NPs exhibits better than dye-adsorbed silica NPs and the FLC was improved with the increase of concentration of doped-dyes. The fluorescent organic dyes were well dissolved in ethanol than DI water. The photostability of dye-doped silica NPs was superior than pure fluorescent organic dye. The FLC of optimized dye-doped silica NPs would be applied to agent of non-invasive fluorescence bio-imaging in live cell and in vivo.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.407-413
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• 2022

This study demonstrates a method for synthesis of amine functionalized and easily size controllable silica nanoparticles through biomimetic polyamine complex. First, we generate a polyamine nanocomplex composed of polyallylamine hydrochloride (PAH) and phosphate ion (pi) to synthesize silica nanoparticles. The size of polyamine nanocomplex is reversibly adjusted within the range of about 50 to 300 nm according to the pH conditions. Amine groups of the PAH in the nanocomplex catalyzes the condensation reaction of silicic acid. As a results, silica nanoparticles are synthesized based on nanocomplex in a very short time. Finally, we synthesize silica nanoparticles with various sizes according to the pH conditions. In the process of synthesizing silica nanoparticles, polyamine chains that act as catalysts are incorporated into the inside and surface of the particles, subsequently, amine groups are exposed on the surface of silica nanoparticles. As a results, the synthesis and surface modification of silica nanoparticles are performed simultaneously, and the silica nanoparticles introduced with amine groups can be easily synthesized by adjusting the sizes of the silica nanoparticles. Finally, we demonstrate the synthesis of functional silica nanoparticles in a short time under milder conditions than the conventional synthetic method. Furthermore, this method can be applicable to bioengineering and materials fields.

• Journal of the Korean Chemical Society
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• v.67 no.6
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• pp.420-428
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• 2023

Crosslinking was introduced into vinylized-mesoporous silica and recycled polyethylene. By introducing a vinyl group into the mesoporous silica, it becomes a material capable of inducing cross-linking with non-polar polyethylene. By synthesizing vinylized-mesoporous silica and inducing crosslinking with recycled polyethylene, a recycled polyethylene composite with improved physical properties than existing recycled polyethylene was synthesized. In addition, even when a small amount is added according to the grade of recycled polyethylene using vinylized-mesoporous silica, the crosslinking reaction proceeds and all physical properties are improved. Four types of vinylized-mesoporous silica were synthesized, and the shape, microstructure, and functional groups were analyzed by TEM, BET, FT-IR, and XRD. Using vinylized-mesoporous silica, three types of compounds were blended by crosslinking reaction with recycled polyethylene. In order to confirm the presence or absence of crosslinking, analysis was performed using XPS and FT-IR, and physical properties such as tensile strength, elongation, flexural strength, and flexural modulus were confirmed using a universal testing machine. As a result, by applying vinylized-mesoporous silica to recycled polyethylene in various grades, the weak physical properties of existing recycled polyethylene were overcome. By applying the vinylized-mesoporous silica, recycled polyethylene composite material that overcomes the weak physical properties to the normal polyethylene, it shows the optimal physical property index that can be used commercially. Therefore, it is expected that it can potentially increase the use of recycled polyethylene and recycle resources.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2519-2525
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• 2014

WeI have studied the process for synthesizing porous silica with a specific surface area of minimum $800m^2/g$ by adding surfactant [Poly Etylene Glycol(PEG) and Hydroxy Propyl Cellulose(HPC)] to the sol-gel reaction between sodium silicate and hydrochloric acid. NaCl, the by-product of the sol-gel reaction, was water cleaned and removed; when 200 ml of water was used to clean 50 g of silica gel, NaCl remaining in the silica gel was reduced to maximum 0.81wt%. The appropriate level of surfactant for silica gel synthesizing proved to be below 5%. As a result of the experiment, for the silica synthesized by adding surfactant of HPC(2.5%)+PEG(2.5%), the surfactant area was $860m^2/g$ and grain size was $20-50{\mu}m$. From this study, we have concluded that it is of industrial significance that specific surface area is improved and silica of a regular grain size is obtained just by adding surfactant in the gel process or drying process of silica.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.6
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• pp.673-679
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• 2008

In this study, Mesoporous silica were prepared from hydrothermal synthesis using gel mixture of tetraethylorthosilcate (TEOS) as silica source and cetyltrimethylammonium bromide(CTMABr) as a template. In the optimum synthesis cause, molar ratio of template and silica changed. The surface and structure properties of Mesoporous silica were determined by XRD, SEM, and BET. N$_2$ adsorption isotherm characteristics, including the specific surface area(S$_{BET}$), total pore volume(V$_T$), and average pore diameter(D$_{BJH}$), were determined by BET. Also, the adsorption character of Pb(II) and Cd(II) ion on Mesoporous silica were measured using ICP. As a result, a SBET of 100$\sim$1,500 m$^2$/g was determined from the N$_2$ adsorption isotherm. Also, the average pore diameter of 2$\sim$4 nm. The adsorption of Pb ion and Cd ion on Mesoporous silica become different depending on the pH of solution. The adsorption amount of Mesoporus silica had higher than that of silicagel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.165-182
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• 2006

In this study, field test was performed to investigate the strength-improvement effect of shotcrete mixed Micro-silica fume and shotcrete quality was estimated by EFNARC standard. Deterioration test combined the Freezing-thawing and Carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of test, the compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. And the strength-improvement effect of strength by silica fume addition ratio of 7.5~10% for cement mass was more superior to the others. Due to relative dynamic modulus, mass decrease rate and carbonation progress of shotcrete mixed Micro-silica fume, it was especially realized that Micro-silica fume reduced deterioration caused by steel fiber and improved a long-term durability of shotcrete.

• Polymer(Korea)
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• v.34 no.5
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• pp.424-429
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• 2010

The hybrid composites of aliphatic polyester-silica were prepared via a sol-gel reaction and their potential application using as a buffer coating layer in the thermoelectric device were investigated. When aliphatic polyesters were thermally treated at a high temperature of $240^{\circ}C$, the polymer showed an increases in thermal degradation temperature by $30{\sim}90^{\circ}C$ according to the thermal treatment time. The polyester-silica composites showed an increases in thermal degradation temperature by $30{\sim}50^{\circ}C$ according to the content of the added silica. Polyester-silica composite showed neither discoloration nor change in optical properties because Knoevenagel condensation reaction was hindered by silica structure. The thermal conductivity of the composites increased linearly according to the content of added silica.

• Applied Chemistry for Engineering
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• v.1 no.1
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• pp.63-72
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• 1990

Surface of crystalline silica was sequentially reacted with silane(A 187), liquid rubber(CTBNx8) and vinyl monomer(AA, MMA, 2-HEA, GMA) in existance of amines(TEA, CTMAB, BETAC) or peroxide(BPO). By mixing it with epoxy resin at a ratio 0~36%(volume %) of total component, liquid properties of mixtures was investigated experimentally. i) Coating ratio depended on quantity and sorts of catalyst. ii) Total coating of 2.5~5.8% was attained by using 0.1~2.0% of catalyst. iii) Treated surfaces represented each different features in according to sorts of treatment. iv) Silane/rubber or silane/rubber/vinyl represented lower viscosity and settling than non-treated or silane-treated.